Noise abating means for pressure liquid orifices



L. E. ROENICK May 17, 1966 NOISE ABATING MEANS FOR PRESSURE LIQUID ORIFICES Filed Feb. 12, 1964 Emil/w United States Patent 3,251,434 NOISE ABATING MEANS FOR PRESSURE LIQUID ORIFICES Lester E. Roenick, Toledo, ()hio, assignor to Dura Corporation, Oak Park, Mich, a corporation of Michigan Filed Feb. 12, 1964, Ser. No. 344,368 1 Claim. (Cl. 181-36) This invention relates to hydraulic cylinders in general, and more particularly to improvements in hydraulic cylinders including means for minimizing audible noise in the transfer of fluid in such cylinders.

There are a number of areas of improvements to be considered in hydraulic cylinders. Notable among these areas are greater ease and less cost in the manufacture and assembly of a piston head on the end of a piston rod. Also, there is the problem of snubbing the force of the piston travel near the end of its stroke. And another area due consideration is the problem of eliminating audible noise in the transfer of fluid in a hydraulic cylinder.

As will be appreciated, it is desirable that hydraulic cylinders which are used as part of a power package in the operation of certain mechanisms, as for example hospital beds and the like, be as noiseless as possible. Surprisingly, the transfer of hydraulic fluid in a hydraulic cylinder can create audible noise which is most disconcerning and its elimination is most troublesome.

One of the causes of audible noise in the transfer of hydraulic fluid in a hydraulic cylinder is the mis-matching of orifices through which the fluid is required to flow. If a pair of spaced orifices are not matched reasonably close, and the downstream orifice is the larger of the two, there is an audible noise created which may be amplified by the disposition of the orifices in the cylinder and is most distracting and annoying.

Those that manufacture and assemble hydraulic cylinders make every effort to hold parts to close tolerances and to match parts required to have complementary fluid flow orifices. However, this is rather expensive because of scrap losses and labor costs. Furthermore, despite the best efforts made in this regard, mis-matching occurs occasionally and, as always seems the case, it is usually when minimum noise is of prime importance.

It is an object of this invention to provide a hydraulic cylinder with several noteworthy improvements.

It is an object of this invention to provide a better means of making and assembling a piston head on a piston rod for use in a hydraulic cylinder.

It is an object of this invention to provide means for snubbing the piston near the end of its stroke.

It is an object of this invention to provide means for eliminating audible noise in a hydraulic cylinder due to the mismatching of rfluid passage oriflices.

:In this latter regard, it is an object of this invention to provide baflle means within the flow passage of hydraulic cylinders to eliminate the necessity for close matching of fluid passage orifices and to prevent audible noise.

It is an object of this invention to provide means for eliminating audible noise due to mis-matched fluid passage orifices in fluid cylinders and which is sufficiently simple that it may be made as a field change to hydraulic cylinders presently in service.

More specifically, it is an object of this invention to provide a noise inhibiting fluid flow bafile for use in hydraulic cylinders and elsewhere and which includes a conical recess provided on the exhausting side of a pair of fluid orifices, normally required to be closely matched, and a small disc with a pair of spaced orifices, together matching reasonably close in area the area of the orifices 3,Z5l,434 Patented May 17, 1966 mentioned, for causing turbulence in the exhaust flow and precluding the noise otherwise present.

These and other objects and advantages in the practioe of this invention will become more apparent upon a reading of the following specification in regard to a preferred embodiment and having reference to the accompanying drawings.

In the drawings:

FIGURE 1 is a vertical section of a solenoid-operated and valve controlled hydraulic cylinder incorporating the features of this invention.

FIGURE 2 is an enlarged and cross-sectional view of a fragmentary part of the cylinder shown by the first drawing figure for more clearly shown the noise inhibiting bafi le of this invention.

FIGURE 3 is a bottom plan view of the bafile shown by the last mentioned drawing figure as seen in the plane of line 33 thereon.

FIGURE 4 is an enlarged detail of the piston of the hydraulic cylinder shown by the first drawing figure as seen in the plane of line 4-4 thereon.

FIGURE 5 is an exploded isometric view of the parts of the noise inhibiting baflle of this invention.

In the embodiment shown, the hydraulic cylinder 10 includes a tubular body portion 12 crimped at one end to a casting 14 which provides a closure and includes a fluid passage 16 therein. The other end of the tubular body member 12 is crimped in engagement with a casting 18 having an axial bore 20 provided therethrough for the piston rod 22. A suitable seal 24 and felt wiper 26 are provided in the bore 20 and are receptive of the piston rod 22 therethrough.

A piston member 28 is provided on the end of the piston rod 22 and in the chamber space 30 provided within the tubular body member 12. The pistol member is made of two parts 32 and 34 which are fitted together in the cylinder body and are formed to provide an annular groove 36 therebetween for an O-ring seal 38.

The piston rod 22 has its inner end formed to receive one of the piston member parts 32 into shouldered engagement therewith and the other member into preassembled bayonet fixed engagement there-with by means of a bayonet type slot 40 in the other piston member part 34. This avoids the screw threading operation previously required to prepare the piston rod to receive a one piece piston in nut held engagement therewith.

The head end 42 of the piston rod, while reduced in size relative to the shank of the rod, is made large enough to pass through a receptive hole 44 in the first piston part 32 and the larger part 46 of the bayonet slot 40 in the other piston part 34. However, only the reduced section 48 of the rod, spaced from the terminal end, will pass into the smaller end 50 of the bayonet slot. The terminal end of the piston rod then forms a head holding the piston parts together and in shouldered engagement with the rod.

When the piston 28 and rod 22 are in the cylinder, the bayonet slotted piston part 34 is held centered on the rod and disengagement from the rod is impossible.

Loosely surrounding the piston rod 22 is provided an annular member 54 which has slight clearance with respect to the rod and to the inner wall of the tubular body member 12. It is held in spaced relation to the piston 28 by a conical spring 56 which is attached at its smaller end to the piston rod 22. This member may be formed of plastic or any other suitable material and is shaped such that upon engagement with the end casting 18 it will seal ofi" the chamber space 58 from normal fluid flow to the passage 60 provided therein. This occurs only when the piston and rod are near the end of their extended stroke.

The annular member 54 is provided with a radially disposed bleed passage 62 to permit fluid to bleed into the chamber space 58 via the clearance space around the piston rods when it is otherwise in sealing engagement over the chamber space 58. This has the affect of permitting movement of the piston towards the end casting 18 after the annular member is engaged therewith but at a very slow rate and one which may be varied to suit conditions of operation by varying the size of the bleed passage 62.

It will be appreciated that the bleed passage 62 may be in the form of a single hole or a plurality of holes disposed for communication with the chamber space 58 and as necessary to provide the amount of fluid bleed desired. Similarly, the length of the spring 56 may be varied, or made lighter or stronger as desired, to provide control of the piston movement over any desired portion of the piston stroke and particularly near the end thereof.

A solenoid coil 64 is provided in one end of the cylinder and is receptive of a passage member 66 provided centrally therethrough with a solenoid operated member 68 provided therein. The passage member includes a fitting 70 threaded into the end closure 14 and a tubular memmer 72 in sealed engagement therewith. The tubular member 72 provides a chamber space 74 within which is disposed the solenoid operated member 68. The latter serves as a flow control member as will be subsequently shown.

A fluid flow passage 76 is provided through the fitting 70 and is in communication with the passage 16 to provide fluid access to the chamber space 74.

The solenoid operated flow control member 68 is formed to include an axial flow passage 78 and communicating cross-passage 80. A return spring 82 is provided in the axial flow passage and serves to position the solenoid operated flow control member 78 when the solenoid coil 64 is deenergized.

A casting 84 is provided in one end of the cylinder to separate the solenoid coil 64 from the chamber area 30 which has the piston therein. The casting 84 is formed to receive a valve seat member 86 in cooperative disposed relation relative to the solenoid operated flow control member 68. The valve seat member 86 is held in place by a fitting 88 which is receptive of the end of the tubular member 72 and is threaded into the casting 84. It also provides a chamber space 90 which communicates with the cross passage 80 in the solenoid operated flow control member.

An orifice 92 is provided through the valve seat memher. It is normally closed by the solenoid operated member which is held in engagement therewith by the spring 82 when the solenoid coil is dcenergized. A conical recess 94 is provided under the orifice 92. A recess 96 is provided in the face of the valve seat member and a disc 98 is received therein. A pair of holes 100 and 102 are provided in the disc 98.

A passage 104 is provided through the casting 84 by an orifice fitting disposed therein. The orifice passage is in communication with a chamber space 108 provided next adjacent the piston 28.

Suitable electric leads 110 are connected to the solenoid coil 64 and are operative in energizing and deenergizing the coil as desired to unseat the solenoid operated flow control member 68 and to allow fluid to flow into the chamber space 108 and upper end of the larger chamber 30 to actuate the piston. The fitting 70 will be appreciated as including an orifice 1 12 which is normally required to closely match the orifice 92 to prevent noise in the flow of fluid through the hydraulic cylinder.

When the solenoid coil 64 is not energized the spring 82 holds the solenoid operated flow control member 68 on the valve seat member and closing the flow orifice 92. No fluid will flow into the upper end of the chamber space 30 to actuate the piston and motivate the piston rod.

When the solenoid coil 64 is energized the solenoid operated member 68 is drawn into the coil and away from the valve seat member to open the flow orifice 92. Fluid fiows through the passages 16 and 76, the orifice 1:12, passages 78 and in the solenoid operated members, into the chamber space and through the valve seat orifice 92.

The through flow of fluid is interrupted by the baffle disc 98. The two holes and 102 in the disc require that the flow be split and pass through both of them to the piston retaining chamber space 30. Further, the conical recess 94 induces a turbulent flow which is moderately restrictive and assists in breaking the sonic aflect that would otherwise be present. The two holes will be appreciated as together being relatively equal in area to that of the orifices 92 and 1 12 which are themselves as close in area to each other as is practical. No purposeful flow restriction need be provided in the system.

Fluid entering the chamber space 108 and the larger chamber 30 acts on the piston head 28 and moves the piston rod 22 out through the bore in the end fitting 18.

Upon engagement of the annular member 54, disposed about the piston rod, with the end fitting 1 8, the chamber 58 will be sealed ofl except for the flow through the bleed passage 62 thereby causing the rate of travel of the piston and rod to be slowed during the last portion of the piston stroke. The continued application of fluid pressure will cause the piston to continue its travel until it bottoms and the spring 56 is fully compressed.

The latter in no way inhibits full power application in the retraction of the piston and rod within the cylinder.

From the foregoing, it will be appreciated that a much more simple and less expensive piston rod and piston head assembly has been proposed. Further, such an arrangement in the disclosed combination reduces costs sufficiently in one respect to enable improvements in other respects; though the other improvements suggested are themselves very nominal in cost.

The bleed-down snubber disclosed may be used in the combination disclosed or elsewhere end, as mentioned, may be varied to suit whatever need arises.

The noise inhibiting baflle means disclosed is most noteworthy in its extreme simplicity and is obviously adaptable for use in other instances for like purposes. However, it is particularly suited for the use disclosed in that it is formed as a cooperative part of the system and requires but slight modification of existing parts and the addition of one inexpensive simple part to complete the assembly.

Although a preferred embodiment of this invention as regards improvements in hydraulic cylinders has been shown and described, with particular emphasis on certain individual features, it is to be understood that the overall combination and the individual features are both to be considered along with such variations and modifications therein as are within the spirit and scope of the teachings set forth and enunciated in the hereinafter appended claim. Further, the language of the appended claim to be considered as drawn to the combination or individual features to the extent of the broadest interpretation due the language used and are not to be otherwise limited unless specifically excluded thereby.

Iclaim:

In a pressure liquid system including a liquid flow passage, a pair of spaced flow restricting orifices in said liquid flow passage, each of said flow restricting orifices generally having equal areas, arid noise abatiug meansin said liquid flow, passage, said noisezibitifig means including a 'turbulent flow producing chamber in said liquid flow passage, said chamber being in the shape of a truncated cone and the smaller end thereof having a diameter equal to the diameter of its adjacent flow restricting orifice, and fluid flow dividing orifice means in said liquid flow passage and in direct communication with said chamber,

said flow dividing orifice means being positioned across said liquid flow passage at the base of the conically shaped chamber, the sum of the areas of the orifices in said fluid flow dividing means being substantially equal to one-half the sum of the areas of said pair of flow restricting orifices.

References Cited by the Examiner UNITED STATES PATENTS 425,619 4/1890 Murphy 18133 498,802 6/1893 Lohbiller 251-127 X 1,140,653 5/1915 Barnstead 2s1 127 1,180,777 4/1916 Lemp 92-172 Rogatchoif 92-172 Sloan 18l133 Miller 18 1-33 Freed 181-33 Samiran 251127 X Graham 181--33 Woodlinry 18146 Hallene 18146 10 LEO SMILOW, Primary Examiner.

K. J. ALBRECHT, Examiner.

R. S. WARD, Assistant Examiner. 

